Ton-mile recorder

Abstract

An improved ton-mile recorder for accurately measuring the work done by a cable of a drawworks system. Analog signals representing weight applied to the cable and pulse signals representative of cable movement are integrated electronically to provide electrical gate pulse signals that represent work done by the cable. A high degree of accuracy of the resulting work indicating pulse signals is accomplished by synchronizing a gate pulse of predetermined duration with a pulse train, the frequency of which is representative of weight applied to the cable. A proximity detector is employed to detect the various evenly spaced bolts of a bolt circle of the typical drawworks clutch which rotates along with the cable drum. As each bolt passes the proximity detector, a pulse signal is transmitted which indicates a segment of drum movement and thus a segment of cable movement.

Description

IN THE DRAWINGS

FIG. 1 is a mechanical schematic illustration of a drawworks drum and block and tackle system such as is typically employed by oil well drilling rigs.

FIG. 2 is a combination mechanical, hydraulic and electrical schematic diagram illustrating developing of pulse and analog signals relating to cable movement and cable weight, together with apparatus for processing the electrical signals to perform such integration thereof as to yield electrical signals representing work done by the cable during use.

FIG. 3 is an electrical schematic circuit that is capable of receiving the pulse and analog signals and achieving integration thereof to develop the cable work indicating signal.

FIG. 4 is an integrator timing diagram illustrating graphical coordination of the signal output of the voltage-to-frequency converter and monostable multivibrator together with the possible development of false pulses and delay of the pulse window of the monostable multivibrator so as to eliminate the false pulses.

FIG. 5 is a front view of a drawworks system showing a bolt circle and showing a proximity pickup supported in position to detect passage of the individual bolts as the drawworks drum is rotated.

FIG. 6 is a side view of the drawworks system of FIG. 5.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring now to the drawings and first to FIG. 1, there is illustrated a drawworks and block and tackle system generally at 10 such as typically employed during drilling and service operations for oil wells. The drawworks system includes a drawworks drum 12 having a length of wire rope or cable 14 spooled thereon. The block and tackle system typically incorporates a crown block generally illustrated at 16 that is mounted at the upper portion of a well drilling derrick and further incorporates a traveling block illustrated generally at 18 that is moved vertically relative to the stationary crown block by means of the cable or line. At one side of the crown block is typically provided a fast line sheave 18 and at the opposite side of the crown block is provided a dead line sheave 20. Intermediate sheaves 22 are employed to accommodate the number of lines that are utilized in the block and tackle lifting system. The traveling block 18 is provided with a plurality of traveling block sheaves 24, the number of which also corresponds to the maximum number of lines that are expected to extend between the crown block and traveling block. The traveling block is also provided with a hook 26 that supports the drill string, well casing or other load being supported by the block and tackle system.

The length of cable extending between the drawworks drum 12 and the fast line sheave 18 is referred to as the fast line which is illustrated in FIG. 1 at 28 and a dead line 30 extends between the dead line sheave 20 and a dead line anchor 32 with the remote extremity 34 extending to a storage reel 36 where fresh cable is stored for future use. As indicated above, it is customary to begin drilling operations with eight lines passing between the crown and traveling blocks to provide an eight to one mechanical advantage. As greater supporting capability is required by deeper drilling of the well bore causing substantial increase in the weight of the dril string and casing, ten or twelve lines may be strung between the crown and traveling blocks for the purpose of increasing the mechanical advantage such as from eight-to-one to ten-to-one or twelve-to-one. As the number of lines is increased between the two blocks, the mechanical advantage increases but the speed of the traveling block decreases.

Because presently known ton-mile recorder systems are not capable of functioning accurately at high velocity cable movement such as 4,000 feet per minute at the fast line, cable movement is typically detected at the slow line sheave 21 of the crown block. By detecting cable movement at the slow line sheave and by introducing a multiplier factor, depending upon the number of lines extending between the crown block and traveling block, ton-mile recorder capability can be accomplished and an accumulated ton-mile display may be provided for inspection by operating personnel. Multiplication of slow line incremental movement, however, is not entirely satisfactory since the resulting total of the calculations is inaccurate due to multiplication of any error that might exist. A further possibility of manual error also exists due to the fact that a manual selection must be made to select the cable multiplying factor, depending upon the number of lines extending between the crown block and traveling block. It is possible that manual errors may also be introduced and multiplied. It is desirable to eliminate the possibility of any manual errors and to achieve detection of cable movement in direct response to fast line movement without employing any multiplying factors that might introduce further inaccuracies.

While working stuck pipe to free it within the well bore, cable loads are repeatedly applied through the block and tackle system of the drilling rig but there is usually only minimal movement of the traveling block because of the stuck pipe. Where cable movement is detected at the slow line, the incremental movement of the slow line is usually too small to measure and thus such cable work does not become accumulated by the ton-mile recorder. It is desirable to detect fast line movement in the order of about three inches to about ten inches with a ton-mile recorder system in order that the work of the cable may be accurately presented even when working stuck pipe or otherwise causing small incremental movement of the cable system. In order for the teachings of U.S. Pat. No. 3,884,071 to be employed for detection of fast line movement in the range of about three inches, ome 754 magnets would be necessarily embedded in a slow line sheave of 60" diameter in order to accomplish the appropriate ton-mile calculations. This, of course, is a practical impossibility, and therefore such devices are not capable of measuring incremental fast line movement when such movement is minimal.

In accordance with the present invention, as shown in FIG. 2, the drawworks drum 12 is provided with a shaft 38 typically extending through appropriate bearings. A gear 40 is connected to the shaft 38 and presents a plurality of gear teeth 42 each of which being representative of a small segment of rotational movement of the drawworks drum and is thus representative of a small increment of linear movement of the fast line section 28 of the cable. A Hall-effect or other metal or non-metal proximity detector 44 is positioned so as to locate the sensor 46 thereof in close proximity to the path of the gear teeth 42. As each gear tooth comes into close proximity to the sensor 46, the proximity detector generates an output pulse in conductor 48 which is in turn coupled to signal processing circuitry 50 for appropriate electronic processing of the signal. The pulse signal generated by the proximity detector is a single square wave pulse for each gear tooth, which pulse also represents an increment of movement of the fast line 28. Alternatively, as shown in FIG. 2, the drawworks drum may often have an appended part 41 attached to its shaft 39 being provided with a quantity of bolts 43 arranged to form a circle. In such case, it is often convenient to utilize the bolt 43 to activate the metal proximity detector 45 which provides an output pulse in conductor 49, which is in turn connected to signal processing circuit 50 for appropriate electronic signal processing.

As shown at the lower portion of FIG. 2, a tension/hydraulic transducer is illustrated generally at 52 which comprises a base portion 54 that is secured to the dead line 30 by means of appropriate clamp elements 56 and 58. A plunger element 60 extending through the base portion 54 is moved responsive to tension applied to the dead line 30, thus causing consequent increase or decrease or hydraulic pressure contained within a hydraulic chamber 62. The pressure of the hydraulic fluid is transmitted via a hydraulic line 64 to a pressure/voltage transducer device 66 that is connected by means of a tee fitting 68 into hydraulic line 64 which ordinarily transmits hydraulic pressure to a hydraulic weight indicating system of the drilling rig. Since most modern drilling rigs incorporate hydraulic weight indicator systems of this nature, it is considered inexpensive to simply tap into this hydraulic line and also transmit the hydraulic pressure to the pressure/voltage transducer. In response to the pressure within the hydraulic fluid line 64, the transducer 66 generates an electrical analog signal in a conductor 70 that is also coupled to the signal processing circuitry 50. The analog signal, which is representative of weight or tension applied to the dead end line 30 is a D.C. voltage that is proportional to the weight being supported by the cable.

The electronic signal processing ciruitry 50 is designed particularly to perform the calculation: ##EQU1## Where: W=ton-miles (work done by the cable)

T=weight applied to the cable

dx=distance of cable movement

The display portion of the circuitry 50 includes a digital counter 72 that is capable of being manually reset and a digital counter 74 that is nonresetable and continuously accumulates data indicating work done by the cable. When new cable is installed in the block and tackle system of the drilling rig, a reading is taken of the nonresetable digital counter 74 and the resetable digital counter is reset at "0." In the event the resetable counter should be inadvertently reset, drilling personnel will be able to calculate accumulated work down by the cable by comparing the total of counter 74 with the reading taken at cable installation. Human error is thus eliminated.

Referring now to FIG. 3, the signal processing circuitry 50 is presented more specifically by virtue of the schematic diagram. The circuitry incorporates a distance input 74 that receives the pulse signals from the proximity detector 44 via conductor 48. The pulse input signals are filtered by means of a resistance capacitance network including resistors 76 and 78 and a capacitor 80. The filtered pulse signals are then processed by means of a Schmitt trigger circuit 82 having the capability of shaping the pulse wave form shown at 84 to the square wave form illustrated at 86. The Schmitt trigger circuitry shapes up the incoming pulse and provides a square wave form having a fast rise time as indicated at 86. The Schmitt trigger circuit is coupled by conductor 88 with a monostable multivibrator circuit 90 having a resistance and capacitance network incorporating a variable resistor 92 and a capacitor 94. The resistance-capacitor network of the one-shot provides a time constant that determines the duration or width of the output pulse.

The monostable multivibrator or one-shot 90 is set by means of the variable resistor 92 such that positive going pulse segments applied to the input thereof will trigger it to produce an output pulse of a certain duration, which output pulse is illustrated at 96. The width of the output pulse 96 must be carefully determined such that at maximum cable speed the pulses do not overlap or become contiguous. For example, assuming that one distance pulse reflecting cable movement is desired for each three inches of cable movement and the maximum cable speed is 4,000 feet per minute, then: ##EQU2## .lambda.=0.00375 sec/pulse .lambda.=3.75 mS

The one-shot circuit is therefore adjusted to produce 3.75 mS pulses by means of the resistant capacitance network 92-94.

The cable weight analog signal which is identified graphically at 98 is introduced at the input 100 of a voltage-to-frequency converter 102 after suitable filtering by a resistance and capacitance network including a resistor 104 and capacitor 106. The voltage-to-frequency converter circuit 102 is provided with a time constant by a resistance capacitance network including a variable resistor 108 and a capacitor 110 and develops a pulse train identified graphically at 112 having a frequency that is proportional to the weight supported by the cable of the drilling rig. The output conductor 114 of the voltage-to-frequency converter 102 is coupled by means of conductor 116 to a "D" type flip-flop circuit 118.

The basic integration (multiplication) of weight takes place as follows: For each incremental distance of cable travel, a pulse is created of predetermined and constant width and is applied to an AND gate 120. Likewise applied to the AND gate is the pulse train created by the voltage-to-frequency converter to represent weight applied to the cable system. For the sake of example, let the weight of the empty traveling block (15 tons) produce a frequency of 1066.67 Hz. For each gate pulse of 0.00375 seconds, four cycles are allowed to pass through the AND gate. The divider is arranged to divide by: ##EQU3## D=67,548 cycles/ton-mile

Thus, the counters are updated by one ton-mile for each 67,584 cycles from the integrator circuitry. It may be easily demonstrated that the constant is valid for any number of lines strung, since the weight (line tension) increases in direct proportion to the reduction in distance when less lines are strung.

Unfortunately, the ideal situation described above does not exist in fact. With reference to the timing diagrams of FIG. 4, it will become evident that at low ratios of weight pulse frequency to gate pulse width, large errors can be developed by the multiplier circuitry due to the effect of false pulses. The output of the voltage-to-frequency converter is illustrated at A while the pulse output of the single shot is shown at B. In view of the fact that the single shot output pulse is not synchronized with the output of the voltage-to-frequency converter the result of A-B And operation may develop false pulses as shown at C. Even though the gate pulse B is only wide enough to admit four pulses, the fact that it is not synchronized with the weight pulses A causes five pulses to appear. The "D" type flip-flop circuit 118 functions to synchronize the gate pulse window with the weight frequency pulse as follows:

The gate pulse is applied to the "D" or data input of the flip-flop circuit 118 and thus the flip-flop circuit is armed to transfer the gate pulse to the "Q" output of the flip-flop circuit at the next positive edge of the weight pulse A that is applied to the "clock" input of the flip-flop circuit. Thus, the gate pulse is delayed to correspond exactly with the beginning of the next weight pulse. Likewise, the gate pulse is stopped in the same manner. The effect achieved by the flip-flop circuit 118 delays or shifts the window established by the gate pulse as shown in comparison of the timing diagrams B and D of FIG. 4. In comparing timing diagrams D and E of FIG. 4, the resulting delay of the gate pulse and correspondence between the gate pulse and the voltage-to-frequency converter becomes clearly evident. The possibility of false pulses is eliminated and thus the accuracy of the multiplier system is increased from 25% (at a four-to-one pulse ratio) to 1%.

It is highly desirable in the manufacture and sale of ton-mile recorder systems to provide equipment that may be efficiently integrated with existing equipment typically found on conventional drawworks systems. Accordingly, as illustrated in FIGS. 5 and 6, there is provided a proximity pickup system for detecting drawworks drum movement, which pickup system is responsive to passage of the bolts of a drum clutch bolt circle of conventional nature and which is present on most drilling rig drawworks systems. As shown in FIGS. 5 and 6, the drawworks system incorporates a skid or base structure 122 having a bearing support structure 124 interconnected therewith and extending upwardly therefrom. A shaft bearing structure 126 is provided at the upper portion of the bearing support 124 and provides rotatable bearing support for the shaft 128 of a wire line drum 130 about which wire line 132 is wound. The drum structure 130 incorporates a drum flange 134 that retains the wire line in proper position on the drum. A drive sprocket 136 is typically interconnected in nonrotatable relation with the drum shaft 128 and a drive chain system interconnects the drive sprocket with a source of motive power that induces rotation to the drum shaft and drum.

The drawworks system also typically includes a drive clutch structure 138 that is interconnected with the drum shaft 128 and presents a plurality of boltheads 140 which are evenly spaced about the drive clutch and define a bolt circle, a part of which is shown in broken line at 142. Although the spacing of the various bolts 140 of the bolt circle 142 will vary to some degree, it has been determined that the spacing of the evenly spaced bolts of typical drilling rig drawworks systems represents approximately ten inches of line travel. Although the spacing of the bolts is substantially greater as compared to the spacing of the gear teeth described above, typical bolt spacing nevertheless represents quite accurate measurement of line travel. Furthermore, since the spacing of the bolts represents line travel which is directly measured without any requirement for conversion of measurement signals to represent fast line movement. Under circumstances where greater accuracy is required, however, the gear tooth detection technique described above may be employed within the spirit and scope of the present invention. It is also within the spirit and scope of this invention to achieve incremental drum movement detection by any other suitable means that enables the detection of suitably small increments of drum movement.

In accordance with the embodiment illustrated in FIGS. 5 and 6, a support post 144 may be interconnected with the drawworks skid 122 and a suitable proximity device 146 will be attached to the upper portion of the post 144 and position with the proximity detector portion 148 thereof in accurate registry with the bolt circle 142. As the various bolts 140 are individually moved into selected proximity with the proximity detector 146, an electrical signal is generated that represents an increment of fast line movement.

In order to install the fast line movement detection apparatus, the only modification that is required to the drawworks system is the attachment of the support post 144 to the drawworks skid 122. This may be accomplished by welding, bolting or by any other suitable form of attachment. Installation is therefore possible with minimal requirement for modification and without in any way interfering with operation of the drawworks system.

Having thus described the invention, it will be apparent to those skilled in the art that various changes and modifications can be made without departure from the spirit of the invention or the scope of the appended claims.

Claims

1. A method of calculating accumulation of work done by the cable of a drawworks system or the like, said method comprising:

detecting incremental rotational movement of the drawworks drum of said drawworks system, there being a plurality of rotational increments for each revolution of said drawworks drum and providing a first electrical signal for each increment of drawworks rotational movement detected;

detecting the weight being supported by the cable said drawworks system during each increment of rotational movement of said drawworks drum, and providing a second electrical signal representative of the weight detected;

electronically integrating said first and second electrical signals and providing an integrated electrical output signal representative of weight applied to said cable and distance of cable movement and indicating work done by said cable during each of said increments of rotational movement of said drawworks drum:

means being rotatable along with said drawworks drum and incorporating a circle of evenly spaced bolts the spacing of which is representative of increments of rotational movement of said rotatable means; and

a proximity detector is positioned in fixed relation and oriented in close proximity to said circle of bolts, said proximity detector generating an output pulse responsive to passage of each bolt thereby as said means is rotated, said output pulse being said first electrical signal.

2. A method of calculating accumulation of work done by the cable of a drawworks system or the like, said method comprising:

detecting incremental rotational movement of the drawworks drum of said drawworks system, there being a plurality of rotational increments for each revolution of said drawworks drum and providing a first electrical signal for each increment of drawworks rotational movement detected;

detecting the weight being supported by the cable said drawworks system during each increment of rotational movement of said drawworks drum, and providing a second electrical signal representative of the weight detected;

electrically integrating said first and second electrical signals and providing an integrated electrical output signal representative of weight applied to said cable and distance of cable movement and indicating work done by said cable during each of said increments of rotational movement of said drawworks drum, said first electrical signal being a pulse signal and said second electrical being an analog signal;:

processing said first electrical signal to develop a square wave shaped signal;

further processing said square wave shaped signal to develop a gate pulse window of predetermined duration;

processing said analog signal to develop a pulse train having a frequency proportional to the weight detected;

processing said gate pulse window and said pulse train to synchronize said gate pulse window with the frequency of said pulse train;

applying said gate pulse window and said pulse train to an AND gate to provide AND gate output pulses reflecting integration of said first and second electrical signals; and

accumulating said AND gate output pulses to reflect work done, by said wire rope.

3. The method of claim 2, wherein said method includes:

dividing said AND gate output pulses and developing AND gate divided output signals; and

introducing said AND gate divided output signals to a signal counting device.

4. A method of calculating accumulation of work done by the cable of a drawworks system or the like, said method comprising:

detecting incremental rotational movement of the drawworks drum of said drawworks system, there being a plurality of rotational increments for each revolution of said drawworks drum and providing a first electrical signal in the form of a pulse signal for each increment of drawworks rotational movement detected;

detecting the weight being supported by the cable said drawworks system during each increment of rotational movement of said drawworks drum, and providing a second electrical signal in the form of an analog signal representative of the weight detected;

electronically integrating said first and second electrical signals and providing an integrated electrical output signal representative of weight applied to said cable and distance of cable movement and indicating work done by said cable during each of said increments of rotational movement of said drawworks drum;

processing of said first electrical signal by means of a Schmitt trigger circuit to develop a shaped signal;

processing of said shaped signal by means of a monostable multivibrator to develop a gate pulse window of predetermined duration;

processing of said analog signal by means of voltage to frequency converter to produce a pulse train having a frequency proportional to the weight detected;

processing said output pulse of said monostable multivibrator and said pulse train by means of a "D" type flip-flop circuit to synchronize said gate pulse window with the frequency of said pulse train;

applying said synchronized gate pulse window and said pulse train to an AND gate to develop AND gate output pulses; and

accumulating said AND gate output pulses to reflect work down by said wire rope.

5. The method of claim 4, wherein said method includes:

dividing said AND gate output pulses and developing AND gate divided output signals; and

introducing said AND gate divided output signals to a signal counting device.

6. The method of claim 3, wherein:

said first electrical signal is developed by a metal proximity detector functioning in conjunction with a multitoothed device rotated along with said drawworks drum.

7. The method of claim 3, wherein:

said method step of integrating said first and second electrical signals is accomplished by performing the calculation: ##EQU4## where: W=Ton-miles (work)

T=Weight applied to cable

dx=Distance of cable movement

8. An electronic circuit for automatically and continuously calculating the work done by the wire rope of a drawworks system and providing a display representing an accumulated total of such work, said circuit comprising:

a multi-toothed rotary element being rotated by the drawworks drum shaft of said drawworks system, said multi-toothed rotary element having teeth at least partially composed of metal, the spacing of the teeth of said rotary element defining increments of fastline movement;

a metal proximity detector circuit including a detector element positioned so as to detect the passage of each tooth of said multi-toothed rotary element during rotation of said drawworks drum and said multi-toothed rotary element, said metal detector circuit generating an output pulse signal representing incremental rotational movement of the drawworks drum of the drawworks system, there being a plurality of rotational increments in each revolution of said drawworks drum;

means for generating an electrical analog signal reflecting the weight applied to said wire rope during each increment of rotational movement of said drawworks drum;

means for integrating said pulse and analog signals and developing an integrated output signal representative of work done by said wire rope; and

means for accumulating said integrated output signals and reflecting an accumulated total of work done by said wire rope.

9. An electronic circuit for automatically and continuously calculating the work done by the wire rope of a drawworks system and providing a display representing an accumulated total of such work, said circuit comprising:

means defining an evenly spaced circle of bolts and being rotated along with said drawworks drum, the spacing of said bolts defining increments of fastline movement;

a proximity detector being supported in fixed relation and being so oriented with respect to said circle of bolts as to detect passage of each bolt thereby, said proximity detector generating an output pulse signal responsive to passage of each bolt thereby representing incremental rotational movement of the drawworks drum of the drawworks system, there being a plurality of rotational increments in each revolution of said drawworks drum;

means for generating an electrical analog signal reflecting the weight applied to said wire rope during each increment of rotational movement of said drawworks drum;

means for integrating said pulse and analog signals and developing an integrated output signal representative of work done by said wire rope; and

means for accumulating said integrated output signals and reflecting an accumulated total of work done by said wire rope.

10. An electronic circuit as recited in claim 9 wherein:

a Schmitt trigger circuit is provided; and

said pulse signals are applied to said Schmitt trigger circuit resulting in a Schmitt trigger circuit output of shaped pulses to provide fast rise time.

11. An electronic circuit as recited in claim 10, wherein:

a monostable multivibrator is provided having the input thereof coupled to the output of said Schmitt trigger circuit, said monostable multivibrator being responsive to positive going pulse segments at the input thereof to develop an output pulse of a predetermined duration.

12. An electronic circuit as recited in claim 11, wherein:

said predetermined duration of said output pulse of said monostable multivibrator being such that, at the maximum pulse frequency expected from said metal proximity detector, each of said pulses remains unitary.

13. An electronic circuit for automatically and continuously calculating the work done by the wire rope of a drawworks system and providing a display representing an accumulated total of such work, said circuit comprising:

means for generating electrical pulse signals representing incremental rotational movement of the drawworks drum of the drawworks system, there being a plurality of rotational increments in each revolution of said drawworks drum;

circuit means coupled to said means for generating said first electrical signal and developing a gate pulse of a predetermined duration;

means for generating electrical analog signals reflecting the weight applied to said wire rope during each increment of rotational movement of said drawworks drum;

circuit means coupled to said means for generating said electrical analog signals and developing a pulse train having a frequency proportional to the weight applied to said cable;

means for integrating said pulse and analog signals and developing integrated output signal means representative of work done by said wire rope, said integrating means including circuit means receiving said gate pulse and said pulse train and synchronizing the window of said gate pulse with the frequency of said pulse train;

an AND gate receiving said synchronized gate pulse and said pulse train and having an AND gate output representing integration of said first and second electrical signals; and

means for accumulating said integrated output signal means and reflecting an accumulated total of work done by said wire rope.

14. An electronic circuit as recited in claim 13, wherein said circuit includes:

a divider circuit coupled to the output of said AND gate; and

a counting circuit receiving the output of said divider circuit and providing an accumulated display of divided signals representing work done by said cable.

15. An electronic circuit as recited in claim 13, wherein:

said means for integrating said pulse and analog signals performs the calculation: ##EQU5## where: W=Ton-miles (work)

T=Weight applied to cable

dx=Distance of cable movement